OP is correct - we have not come through with the summoner icon rewards for lifetime RP purchases yet. There have been a few different reasons for the delay, but the good news is that when they do finally come, they should be much cooler than I originally envisioned.
And while I'm fessing up to missing target dates I've put out there, I should mention that the next ultimate skin will not make it in May. Hopefully June! SourceEDIT: There has been no word on what the new Ultimate skin will look like or for what champion it will be, the below image is the old pulsefire ezreal splash art.
It's lonely at the top...