I wouldn't do that because there typically isn't a good reason for a web
service calling wcf service - the two are essentially the same. You would
replace the web service with a WCF service while maintaining the same call
signatures and URLs. If you web service was callable at
www.someservice.com/test.asmx, you would configure your endpoint on your WCF
to be the same so that your clients would not be broken. Underneath, the
implementation of the service would change from web service to WCF, your
clients would not notice anything different, except a huge increase in
performance.

With the COM+ service, i'd be a little more careful. Now, typically, you'd
use COM+ to take advantage of the object pooling capabilities and for legacy
interaction (printing capabilities in a VB/asp web page for instance). If
that's the case, you can replace the service with WCF which provides some of
those functionalities. Otherwise tread carefully. Hands-down you'll see a
drastic performance increase but again, tread carefully on the COM+
replacement. I'm doing an analysis on exactly that this week for a live
project so if you have any more questions, post here.