Yes, Axl did debut in X7, even though it was slightly more frustrating than X6. I hopefully agree, the series after X4 started to go downhill.
There are different plot points that remained unanswered.
1. What happend to Dr. Cain? Why wasn't he featured in X5-Current?
2. What happened to Dynamo? He didn't die, that's for sure.
3. How did X and Zero go from working for themselves to doing Signa's dirty work?
As a Colonel ripoff, he has loads of questioning time.
4. Why wasn't there a Megaman X4.5 game? You know, the story where it answers all the questions in between X4 and X5, how X met Alia and her friends, and so forth. There's just alot of debate going on in that field....