Of course, they'll just pop all those developers, artists and designers out of thin air so they can make two games at once, why don't they!
But no worries, even if they didn't do that, nobody at Game Freak or Nintendo would have any problem at all with a company literally sitting on a finished game that cost them a lot of money to make, just so they can spend just as much time making another game and sell them at the same time, an approach which would likely net them a smaller profit than would have if you sell games individually, when they're finished like everyone else does.
Essentially though it is a very poor decision from a marketing standpoint. Why do you want to confuse customers by trying to sell them two things at once that look similar at first glance but are actually completely different? It's also playing poorly to the attention span of the casual customer - you want to release a game first, then wait until the hype around that dies down before you release your next game. Doing it this way means that you can capitalise on people's tendency to buy things when they're new and highly promoted. If you sell them both at once, you're forcing a lot of people who might only have the money to buy one game to make a choice, and later on when they have the money for another game they may as well end up choosing the latest game that's being promoted then instead.
