And if I had to guess what things will look like in a year these would be my predictions:
Compass will indeed lose the 175s to Envoy - it's already rumored and expected. But, rather than add an MQ base to LAX, watch for YV to shift CR9s there as they get bumped out of DFW and consolidate to LAX with about 20 planes, to backfill the 175, and the rest in PHX.
DFW would then be a clean MQ 175 / 145 and OO 700 base
That would indeed make the 7 carriers predicted - with the end of Compass for Eagle, and put Mesa on notice that they are next ... or else. From there, it's a race, can PSA grow into either ORD or MIA fast enough to free Envoy to go West?
YV won't go back to LAX willingly anytime soon; plus the 175s are required to remain competitive in the market on business routes, there is nothing about a CR9 in some of those markets (like SFO/SMF/PDX/SEA) that is competitive. Also, YV was a terrible operator when in LAX the first round; chronic delays and no MX supportability. Also, YV actually meets goals in DFW, they don't meet them in PHX.
I would predict Compass will end when the contract ends but no sooner. More than likely, you'll see PSA grow in ORD to displace OO rather than MQ such that OO can focus on DFW/LAX/PHX with an all 700 fleet (other than the at-risk/EAS markets) which is in OO's wheelhouse and is their bread and butter area.
And while Mesa may not have a sterling reputation in the business, they are a reliable operator and are able to do so cheaply do to their payscales.
Define reliable... In this day and age, the Mesa CR9 operation isn't even close to reliable. Its not uncommon for them to post a 60% D0 on a blue sky day. On an IRROPS day, they are usually in the 40s. Mesa actually does better in DFW than they do in PHX (and better on the UA front than anywhere on the AA side).
AA is realizing that they are growing the wholly owneds faster than they can keep up so I would expect some more 50 seater retirements along with a short term contract with OO for some more CR7s that are coming off contract with DL.