It's your call as always. If what you have is working and does what you need done - do you need a new camera?
The Pro70 is a bit "old" by today's standards but it is a good camera and you can definitely stick a lot of memory cards in it.
The newer cameras do offer USB plug-n-play with modern OS like WinXP which makes for faster downloads. Personally I use a cardreader so I don't care what kind of I/O interface is on the camera.
If you want more zoom, more resolution and a much faster camera then yes, buy one of the new ones. The Powershot S1 IS
is a great camera, a long 10x zoom with stabilization, 3 megapixels of resolution and a super movie mode - all for $499. It's also smaller and lighter than your Pro70 and runs on regular AA batteries.