Will Software as a Service (SaaS) lead to a wider range of programming languages being used?

I've been reading a lot and giving talks on SaaS and S+S (Software + Services) but the thing most people don't mention is that if you're building a true SaaS application then the only things your customer will ever see is the web interface the API (webservices, REST, ...) which are most likely XML based at this point.  You'll be running the data center where the application lives and won't have to ever worry about deployment at a customer site.  Now there's lots of IT operations benefits to this but as a developer this means you can really write your program in whatever language you want as long it can create the web interface and the XML webservices.  Now this is true even in true SOA models but with SaaS you're pretty much guaranteed that you control the service at all times and are separated by the internet from your customers (rather than partners or other departments in an enterprise).

I'll quote Paul Graham here:

"... when you're writing
software that only has to run on your own servers, you can use
any language you want. When you're writing desktop software,
there's a strong bias toward writing applications in the same
language as the operating system. ... But with Web-based software ... you can use whatever language you want."

This is even more true in the SaaS world.  So, will we see an increase the range of languages used (beyond C#, Java,VB)?  Will the web centric languages (PHP, Pyhton, Perl, ...) be used more for "enterprise" SaaS applications? Will Lisp make a huge comeback ;)