Unless there's some critical reason you need Windows 8, you could always hold on to the license until Apple officially supports it. That being said, people have installed 8 and used the Windows 7 support software to at least get basic functionality in the meantime. It doesn't always work for everyone, though.
And just so you know, a System Builder/OEM version of Windows can be installed as many times as you like as long as it's on the same computer. The license ties to the hardware and is not a "one and done" system. If you're reinstalling the OS all the time, you might have to call MS to activate it, but it's fully automated and takes about 5 minutes.
in terms of updates to win8 then as far as windows8 goes it's running on a normal "pc" not on a mac it's not virtualization here so everything works as normal
I bought an imac 2011 version 22" 4GB ....
I installed windows7 ultimate 64bit on it
since I bought the digital update to windows 8 pro
updated over the internet (you download an exe and take it from there)
it updated fine it use the windows7 drivers so everything in terms of mac stuff works as before
I let it update the amd video card driver and got a lot of crashes at bootup
rolled back to the bootcamp win7 drivers and it's a lot better
sure every now and then startup result in a crash but a reboot always get me into win8
play games and program in win8 never had a cash when I get in and because it's native games run great
likely when the official apple win8 support comes along I will stop getting the odd crash at boot into win8