I don't see why not, the API is available on the SDK to be une on any app.
The real question is would they allow it to do videocalls over the AT&T network??? will they try to charge for it (Like they tried to charge for the 3G calls)??? my guess..is ...no they won't and yes they will try to charge for it.
Well skype did announce that they weren't going to pay for 3G calling, but I can see them charging for 3G VIDEO calling, which would still be lame because it would still be skype-to-skype video calling.
But yeah I'm pretty sure skype on the iphone will eventually be able to use the front facing camera because, as stated, the API is available in the SDK.