I think its more likely than not that the PS3 will outsell the 360 by a big amount till the end of this generation. Could be changed by one successful game but the 360 is essentially dead or falling back outside of America. So if this happens I would say we do not have a "tie". For exclusives: this will depend on the differences in userbase and the ease of ports. But as I said we do not know what will happen.
18 months ago people were saying the Wii doesn't chance a chance against PS3. 6 months ago people on this forum were talking about the PS3 being dead in the water. At the moment you say its a tie between 360 and PS3. I think we should have learned one thing:It is not easy to predict the future.