Oh no, GAFland 1.7 is going to be around for a very long time (once it starts). Jeb has stated before (and again today) that anything generation-wise added for the next couple of updates will also be craftable with current 1.7 generation materials, with regards to block types and such. He truly wants to make changes to chunk generation less necessary, or rather less required, in order to get the "new stuff". Patch 1.7 was the last big changes to biomes we will be seeing for a long time, the next few updatees should be biome unspecific stuff mostly, things like new stuff to craft using 1.7 materials, the mod API, possible new mobs like birds or whales (ambience stuff), etc.
No, once we create GAFland 1.7 it's going to be around for the long haul. If new biome stuff gets added then we'll just have to explore new chunks.
Wait, so are maps limited to the 1.x version they were built in? Or is that only a server thing?