I tried to calculate at what level my prefect Blissey would reach 510 HP. After some calculation I realized that PKM will reach level 80 and only then the CP multiplier will be 100%. So, we can expect some updates to make this happen.
...unless they halve the gains again at level 60 or something.
Besides, there is nothing saying the CpM can't go over 1 (over 100%)
That said, neat little bit of working it all out.
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Every 10 levels the CPM increase per power up is changed and there's no formula for CPM or the change in CPM increase for each 10 levels, secondly there isn't a limit on CPM. It's just a number. It can go above 1, it just means a Pokemon's effective stats are higher than it's base stats.