That's too bad, you're going to miss out on some great improvements over previous versions.
MC 12 probably won't even get started until late this year and the beta may not even appear until spring of next year if past performance is anything to go on.
MC 11, I have to say, is pretty mature. It should be after 290 builds. From here on in, the builds are mainly just tweaks - fine tuning. The list of changes and fixes is now pretty short. I expect the official release almost any day now.
I'm sorry you missed out on the $10 upgrade price, but everybody had over six months to take advantage of it. I did several months ago, but only installed it 8 weeks ago, wanting to wait until it was "mature" enough to use it and not be a beta tester, (I was not dissapointed). MC 11 is completely stable and has been for months.
At $26, it's still a great buy! But you don't have to spend any money to find out, just download itand install it, you'll have 30 days to give it a run for your money at the end of which you can either buy in for that cheap $26 or not.
Try it, enjoy!