Here's the biggest reason for why a GS remake will be made - money. That's the main reason why these games are being made - if they won't sell, they don't make the cut. And I'm very confident that a GS remake is another cash cow waiting to be made.
Platinum... very likely won't have Johto. Firstly - Kanto is closer to Sinnoh than Johto is - would be a very extravegent way to get there, right? The most feasible way would be going through Kanto to get to Johto. Three regions in one game isn't going to happen either IMO.
And then there's the coding - it allows Pokemon from a certain game to say that it came from Johto. There are two spots in the game coding for the such, that are labelled 'JOHTO'. Now, they didn't put coding in the 3rd gens to make it say 'From Orre' for Colo and XD. Instead they just decided to place in 'Distant Land' as the message - so really there is not need to make the coding say Johto int he first place. So why do it? Maybe if a remake is intended.
Jasmine is a slight hint towards it as well. There is really no reason why she has to be there, and give you the Waterfall TM. Anyone else could have done it. Why bring her in, and give a million references to GSC games in Diamond/Pearl as well, when there's no need. I just think that it seems a bit purposful. Not to mention, Jasmine now has a ready-to-go sprite made... hmm.
Ehh, I have to agree with nintendo power on this one, at least. They don't especially need a remake of Gold and Silver, what with all pokemon already accessible by the 4th gen. You know what I'm talking about. What was the *real* reason the made FR/LG? That's right. To put Johto pokemon in the 3rd Gen.
Although I still think a remake or GSC would be nice, it's not looking likely.
Note the new gamers who for them, Diamond and Pearl is the first game for them. Would they rather by an older GBA game, or a new, spiffy DS game that is a remake, but they haven't played yet anyway? There's a need for the Johto and even Kanto Pokes.
What about getting Lugia and Ho-oh, part of dex requirements? Save for XD and Colo - on the Gamecube - or events that to my knowledge don't happen anymore, they won't be able to. And many would be reluctent to get old games just for a few Pokemon. The advantage of a (possible, nor definite, mind) GS remake is the fact that many wouldn't have played it anyway, and many would need the Pokemon anyway.
For me, it's actually looking more likely than not - especially with the first reason that it would make money, without a doubt for me.
