i'd look for folks with inside facts to substantiate, but i'd go along the lines of
1. biggest problem the CTS has is that there is no alpha car under it. hence it has to wear the 'entry-lux' moniker and provide caddy a lower price point. if there was an alpha, caddy could afford to up the price on cts. (motor trend or r&t did a comparo of cts with 5series and Eclass and some others and CTS won. cause they were factoeing price, the cts was loaded while others were not. i suspect if u compare 08CTS with 535 and E350 it would be a pretty good compare and caddy would fare well on merit, agnostic of price.)
re: V8 - yes, when it is available, but it will be a low volume unit. with 304hp from the 6, the 8 is not really needed (shame the CTS names don't convey the engines like bmw and mb - as you know those clowns with the 335 and 545 insist on making sure you know it is not a 328 or 530. (buick prob the only other division with a shot at getting that engine)
2. no freakin clue. i suspect it will exceed the 320hp of the NS, otherwise what is the point!!!
3. STS/DTS will merge and move to zeta (gm4life - don't bother with your DTS needs to stay FWD nonsense again, pls). it will likely be less of a 'sport sedan' and more of a luxury sedan.
shame the platforms couldn't be released at same time, it would make sense to name the alpha caddy the CTS (since BTS name sucks) and name current CTS the STS and have the zeta car carry the DTS label as it would be the spiritual succssor to the deville. (I'd name the 'Son of Sixteen' the Fleetwood or the LaSalle - if it ever came to market and i'd go after the Bentley Continental GT and Flying Spur)