BKGaming: I highly doubt they will remove compatibility options, on the contrary since 10 will pretty much keep the same base it adds more pressure on MS to keep all software compatible. Otherwise they could break windows 10 software that was made before the updates which would not be ideal.
Not at first, but if Microsoft really does continue to iterate on and change Windows 10 then it is conceivable that compatibility with some older titles may break in the name of progress. Keep in mind there are still Win 98 games that work in Windows 8.
Microsoft has stated that updates will be more than just security and include changes and additions to windows itself. Which is fine, if updates were not forced, or if you could opt out of the non-security changes.
Basically its not the security updates that worry me, it is the possibility of Windows itself changing over a long period of time to become something fundamentally different from what it currently is.