First they'll increase the regional pay and work rules more. Then they'll increase the flow. I'd expect it to drop to 1-1.5 years as an RJ Captain, then flow. The could get it down to 2.5-4 years total.
How many will leave the AAG regional for the LCC then if flow to AA is a sure thing in one more year? You'll still have the FO's going to DL-UA-FX-UPS though.

After that, they'll be after the APA for a new B-scale to bring the E175-CRJ700/900 onto the mainline certificate. They'll work a deal that allows Military, 121 pilots with over 5 years experience (or 7,000TT) to direct entry on the larger jets. New civilian pilots or college programs go to the small jets then bid up when their seniority can hold it. A fence to prevent super senior from either side from displacing somebody junior on the other side. Pilots hired after date of merge have no displacement protection (except for large plane not being displaced by small plane, this keeps the direct entry military guys in seat), and eventually when all the old guys retire you have a single list.
tons of little details to address, but the big ideas will probably look something like that.

We had something similar penned out in 2012-2013 between Eagle ALPA and the APA at the time, but the SLI and the addition of two new regionals that didn't play well with others at the time ended it from moving forward. The brass (in Tempe at the time) were okay with it, IF the Maintenance and FA's could reach a similar agreement.

The take away is they will do exactly that once it makes more financial sense.... and that time is rapidly approaching.