I strongly doubt that shutting down the server has anything to do with trying to increase X and Y sales. It simply has to do with having to maintain (i.e. pay) a server infrastructure for just a small subset of people who will continue to play Generation V _AND_ like doing the dreamworld.
Yes, it kind of sucks for those that don't wish / can't upgrade to XY, but the vast majority of customers won't be affected.
My suggestion to the OP is to 'enjoy' the dream world while it is still there. It's quite likely that you'll get tired of it's tedious repetitive nature and shallow mini games long before it goes down.