Well, to that I say no. XHTML 5 would be a continuation of XHTML 1, which is half-bread enough already.
The reason, XHTML 5 probably won't make use of the real reason why people would wish to use XHTML 2 at all, which is, the modularity of XML and all the extensions that go around it.
Syntax is at play here, but a lot more has to do with how applications and other stuff are implemented than syntax alone. The extensions made possible via XML are a huge thing, as well as inovations from HTML 5 such as the canvas element are a huge thing.
So one of thing that I think defines why we should use HTML 5 in the future is how it goes a long way towards being easy to use to make web pages and web apps. XHTML 2 is XML based, and because of XML's construct, a web page might not be exactly at home there. However, XML is a no-question winner when it comes to information sharing such as RSS feeds, but everyone knows there's more than that on the web.