You are way off GL IMO.
WWFE has tried non-wrestling products in the past (one that comes to mind is the WBF, or World Bodybuilding Federation) that failed pretty badly. There's also been Icopro, the nutritional substance, he's thrown concerts and boxing promotions which have gone nowhere either.
None of that however has stopped the WWF from gaining the popularity it's always enjoyed. The WWF have even recently signed lots of new talent with great work ethics and all have the ability to reach superstardom. Financially the WWF is very stable, as they are a billion-dollar company, and even with that being the case most of the XFL investments are from NBC.
But you have a point, if Vince just wants to stubbornly convince all the media out there (which I don't see him doing as he doesn't care at ALL what they think) that it would stick around longer than projected, he will lose much money, and will spend too much time working on it that the quality of the WWF will drop (I know using "quality" and "WWF" in the same sentence is just asking for trouble). In the months leading up to the XFL launch, fans have complained and blame it squarely on the XFL. People have even accused his daughter Stephanie for the somewhat of a failure PPV they put on a few months ago with Survivor Series.
So although I'd like to see the XFL succeed just so those who bash Vince just because he's Vince just shut up, if it's going to harm the WWF, then it should fold.
But Vince is a guy who's taken guys that NO ONE's ever heard of, that people thought would be living on the streets after a few stints into world renowned superstars. Would you believe "The Rock" was once booed out of buildings, because he just sucked badly when he was supposed to play the role of the "good guy". Guys like Steve Austin, Bret Hart, Shawn Michaels were never expected to do anything with their careers, but 20,000+ seat arenas have sold out in minutes just because of the promise that Austin would show up to the show.
And when WCW had Austin, he was essentially a "bench warmer". That was when Vince took a hold of him, and made him bigger than life.