1. How will the future use of DRM (Digital Rights Management) technology be like?
It is likely to increase, possibly with more hardware implementations. Since it must be secret for its own protection, this means a bleak future for media compatibility with open-source Linux and obsolescence for older non-DRM players.
2. What are the factors that will prevent people from using or adopting this in the future?
Customer resistance may be an issue, as may the cost of implementing compared to actual reductions in piracy losses (that is, EXTRA copies sold, not pirate copies prevented). Technical issues my play a wider part, in preventing introduction of methods which would be incompatible with a significant legacy userbase.
3. How common/widely practiced will DRM become in the future?
Where it can be, it will be, though fortunately, it seems that timeshift is still condered to be a legitimate use of broadcast content.
4. Basically, how does DRM work?
While some consider any form of licence to be DRM, the usual context seems to be encoded media, with a decoding player that enforces restrictions according to the licence.