Here's what he had to say:
"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!"
Thanks to Riscion for pointing this one out to me! If you ever stumble across news we may have missed, feel free to toss it over to firstname.lastname@example.org.