Tpw,
Your husband would be absolutely crazy, in my opinion, not to take this opportunity that is being given to him. The "regionals" have peaked out at what they once were, as 50-seat jets are being replaced by fewer 70-ish seat jets. Mainline carrier scope clauses going forward are going to dictate a draw down of some of the regional flying.
As everyone here as stated, this is the beginning of the hiring wave and he needs to jump in now...not wait. Yes, once seniority list integration occurs, hiring will come to a halt for a period of time until the final UAL furloughees decide what they wish to do. As such, your husband will sit near the bottom of the list for a period of time before movement starts up again. Many of us experienced that same situation.
When I had the opportunity to come to L-CAL, I took it. I was in the top 10% in seniority of my previous carrier, a regional. I had the schedules I wanted, could avoid the places I hated, and was making decent money for my situation. In the end, though, a regional is not where I wanted to be for my career. I had to take a more than 50% pay cut to come to L-CAL. Yes, the first year was difficult, but it has been worth it and will only get better.
While you are there to support him and will respect his decision, I would also say this is a decision that you two need to make together as a family. Even ALPA has "family awareness" events for a reason: we are not in this alone and are not the only ones affected by the job. I'd strongly encourage him to read these responses and listen to the advice of others to take the job.
I also agree that getting based on the west coast is very likely within two years. It will end up being more junior than EWR if you ask me.