Most of your questions are answered here:
https://steemit.com/steem/@steemitblog/final-review-of-steem-economic-changesTo answer your question about the powering down process, it is incremental with 1/13 powered down per week. The remaining portion stays powered up and continues to earn vesting rewards (as well as retaining voting rights, bandwidth rights, etc.)
There is fixed no cap on the supply, though the rate of inflation will eventually reduce to 1%.
If you have other questions after reading the above, please let me know.
@smooth, Thank you so much for your help, that post was really helpful.
I bought a solid amount of steem and powered it up. I have been looking on steemd and I can see my vests however it doesn't seem like I'm generating new ones. Steemd is apparently on maintenance for a while so that might be the reason why. Is there a reason that steem is disabled on polo ? I have 1k steem stuck over there that I was not able to withdraw.
Steem appear to be pretty fascinating and I believe these inflation changes are sustainable and beneficial to the holders.
I actually have another interrogation, after reading about the consensus on steem, it doesn't seem worth to me to be a witness or miner, as most of the blocks are generated by the top 19 witnesses, 1 is by a backup witness and 1 is by a miner on the PoW channel.