Will it last longer than the Alliance of American Football (or the previous incarnation of the XFL)?
Yes.
For one, Vince McMahon's set aside about four times as much money, enough for at least three years. And unlike the AAF, which put its faith in a shady investor who ended up getting his accounts frozen, McMahon's funding the league himself and has already put the cash in. Plus, he's not paying for TV like the AAF did: ESPN, ABC and Fox (big networks in and of themselves) are all giving him free airtime. So that saves a few million dollars right off the bat.
Second, barring a spectacular flameout, this XFL won't be anything like the old XFL. For one, the old one came about during the "Attitude Era" when trash was king while violence and sex ruled the day... but in the end, the football was boring, slow and tacky. This is going to be football. It's going to have some quirks, but on the whole, it's football. They actually went through the process of testing the rules changes this past year so that they know what they're getting. So unlike the old XFL, which got a lot of eyeballs but then turned a lot of people off, this is probably not going to have that "yuck" factor that turned so many people off the old XFL.
The players being bandied about for this league are all largely NFL backups with at least some modest success. Ryan Mallett is another one that's likely going to play this coming year. He had some modest success as a backup in Baltimore, a little less in Houston. I think the best comparison one can make for those old enough to remember it is USFL level, before they started going crazy and signing all those huge stars. The talent's probably going to be a step above the AAF, though a few names such as Trent Richardson and maybe Johnny Manziel are getting bandied about for the XFL, too.
Whether it can last beyond those three years and get a stable financial stream is another issue altogether.
