No. It's been nearly 12 years since Misty left the series so kids watching the show today would not even know the character. The reason Serena is written with a crush on Ash is because it's been so many generations since Misty has been gone that they can do the whole female crush on Ash aspect for today's kids as it won't matter.
Whether Misty will ever return again or not is up to writers, but thanks to today kids having all kind of access to internet through traditional way by using PC,or ipod, mobile phones, social networks like facebook i think it cannot be ruled out possibility of new generations being familiar with older characters.
There are also reruns of older sagas on TV channels like Cartoon Network, Boomerang, Get TV etc, accompanied with games and relatives who might got them familiarized with it.
Either way i actually would have liked to see Misty and Serena meeting.
Both have several intriguing sharing points in feeling something which appears to be more than friendship toward Ash, are known to be very smart coming up with conclusions, solutions to problems and how to figure something out on their own and have similar path through which they left family to follow their own interest forming their own life rather than living under someone restrictions. Making it all that more interesting to see how those two would cope with differences learning to develop close friendship .
Misty headstrong, playful and feisty nature knowing how to stand up for herself and others could help Serena to become more proactive, develop interest for career she wants to follow and be more confident and assertive taking role in action. While coming with peace of acknowledging how they both might have share same interest when love is in question possibly leading to initial frustration,and conflict leaving both girls in disbelief. Only to see it later growing in sympathy and understanding from Misty character and vice versa knowing how its like to be in such position.
All the possibilities.
I suppose the writers have just run out of things for the female character to do, she is the 5th girl of the series and by now they've done everything they can between the previous 4 girls.
I don't necessarily think that writers have "run out of ideas". They are simply trying to do something different with Serena character and create entirely new conception through which female protagonist would develop.
In sense of introducing character which is unsure himself of where he belongs, what kind of career he would like to pursue and where he stands in world he is living. Which applies to Serena representing insecurity, lack ofsubstance and cognition in knowing what truly makes her happy seeing herself in that.
Representing problems and fears many of teenagers and kids(even adults sometime) are faced with when trying to figure out what school they want to enter, if they want to go to college, what job they would like to do in future going through soul searching until they discover what is their talent and interest.
Its rather unique and somewhat realistic approach writers may have been taking with Serena character.
Which could open foundation for Serena trying out various activities, careers and occupations related both in utilizing pokemon or sanding your own skills. By learning how to be better cook, costume designer and all kind of other things. Leading to character going through selfquestioning, doubts and fears of what is her true purpose and place in world.
Serena personality also seem relatively different from what was showed with other females respectively so far. Misty is more hotheaded, strongwilled and romantic as person, May is bubbly, at times naive and kind, Dawn is energetic and optimistic, while Iris was more of a hyperactive and cynical in demeanor. But Serena is in comparison much more quiet, shy and reclusive in characterization. Type of character which often tends to keep herself on distance lacking determination and initiative to take charge of something. Coming of as very polite, nice and oriented toward fashin type of person,barrting rare instances of being saucy when irritated to point of losing composure like those instances with her mother (Grace).
Which can be both bad or good depending on what kind of personality you prefer and what traits, play of with other characters and atmpsphere he/she provides suits to your own taste the most.
However whole idea of Serena going as character through idea of soul searching trying to find her own calling can only work if she becomes less dependant on Ash character and finds something elde to identify herself with than just trying to be romantic interest. Considering how recipe for strong and successful character lies in having its own motives, purpose behind existence.
To have character end unfolded out expanding on background, personality, relationship with other characters, whatever flaws she might have and eventually dreams which serve as vector, driving point making her prompt to improve, work on bettering herself and realize in what direction she should go. Which was applied to two examples whbich also had romance subplots going for them(Misty and May), but at same time had their own identity and things which defined them standing in their own right. Thus coming of as strong characters and individuals.
Hopefully same route writers will take with Serena character, because at end of the day while there exist anime where love aspect is driving force of story through which characters can discover their own substance and courage helping them to develop, thanks to expansion on relationship which move things forward. Pokemon is entirely different show having its limitations and enough complex plot to allow to take protagonists through such route on more groundbreaking level.