Yeah def not trying to 'convert' if anything im looking to buy bigger knowing the inevitable swap in the future...I dont know the answer but looking at fox's site it leads me to believe they are actually 2 different forks (650 and 26). To your point I am not sure the extra height would bother me a bit.I thought the 34 was already compatible? Could be wrong...
I'd say it depends on whether you will or won't mind the tiny bit of head angle increase. I honestly wouldn't buy a fork to "convert" as you won't have full tire compatibility. I can't run nobby nics on my current fork, but those are supposedly huge.