Actually, he would have won 7 consecutive Wimbledon titles, since he bounced back to beat Roddick in '09.
I would hesitate to say winning that match would have altered any future outcomes and here's why...
1. Based on his career, I don't think Federer's competitive drive to win slams changes much based on wins or losses.
2. I don't think Federer lacked for confidence in Australia due to his close loss at Wimbledon. He played quite well in that match, arguably as good or better than he did at Wimbledon.
3. I don't think losing the Wimbledon final would have affected Nadal much either. He has proven throughout his career that he can handle tough losses and come back strong.
Both guys have been steady in their careers. They don't need extra motivation. Their desire to win is pretty constant.
So, to me, if Federer won in '08, that's the only outcome that would be different. He'd have 7 straight Wimbledon titles and 8 total, while Nadal would have one in five finals. Slam count would be 18-13.