I FINALLY got my 9-month old to sleep past 6am after months of 5-5:30 wakings and trying everything. We tried earlier bedtime, later bedtime, more naps, less naps, more food, etc. In our situation, limiting naps too much actually made the situation worse.
The ONLY thing that seems to have worked for us is pushing her whole routine forward. For example, she still naps about 3.5 total hours during day and really seems to need it - she's a very active baby. But now she also gets 11 (or at least 10.5) hours at night. But we don't let her first nap start before 9:15 and preferably not before 9:30. We'll let her sleep up to 2 hours at that nap if she wants - as the morning nap tends to be her best one. Then we keep her up at least 3.25 hours, sometime 3.5 hours and her next nap starts around 3 and we wake her at 4:30 and bedtime is between 7:45-8. We've been doing this for some time now and for the past few weeks she's sleeping until at least 6:30 - sometimes closer to 7.
Keep in mind also that at this age many babies only need 11 hours night sleep - and many go back to 11.5-12 hours after one year old.