git has support for a number of other revision control systems too. and i hope some of those other systems will also be able to support different systems. (most of them seem to support svn)
the trend that i believe this should head into is that all revision control systems (well at least the distributed ones) can interoperate with each other, so that anyone may choose the tool they like best, and in the end there may even be a common revision control network protocol in some standard form, that allows transfering changesets back and forth. like we have it with smtp and mail servers and clients. (it's a dream, but who knows :-)
greetings, martin.