While I understand those that point out the dangers in upgrading in production when everything isn't fully compatible, this isn't really the point, and there are times where it's not avoidable. I'll use my company as a recent example: we have been tendering for a contract and subsequently we quickly had to encrypt all of our machines. As a rule we are on Windows 7 Pro with a few on 8. Bitlocker is far from ideal, but in any case we couldn't use this on our Win 7 machines - it's only available on Ultimate and Enterprise and it's all but impossible to upgrade to these now. We decided to use Truecrypt instead for the bulk of the machines, however some have GPT partitions and therefore are not compatible with Truecrypt. In these cases, we could think of no other solution than upgrading to Windows 10 Pro and using Bitlocker. We've done this, but now we have the Avast issue to deal with.
I agree we should be able to expect that Avast is ready by now, especially given the time frame since 10 was released, and especially especially because their non-paying customers have been taken care of. We pay a lot of money to Avast and if they are going to fail to deliver so spectacularly, then I think we have the right to expect better communication from them on it, as pointed out by others.
Our licenses expire in April and as the sole decision maker on which AV we use, I can guarantee we will not renew our 30+ licenses.