I'm not sure on this either. I'll ping a fellow Rioter to answer this. My knowledge comes from putting this video together unfortunately. Sorry!
All the changes hit at the same time - so you'll receive blue essence for your old runes and runepages, not ip. It'll be the same value as the numbers in this video (100 blue essence for tier 3 marks, seals and glyphs and 300 blue essence for each quint), but you won't be able to spend it before it gets converted.
RiotCalad
All the changes hit at the same time - so you'll receive blue essence for your old runes and runepages, not ip. It'll be the same value as the numbers in this video (100 blue essence for tier 3 marks, seals and glyphs and 300 blue essence for each quint), but you won't be able to spend it before it gets converted.
Hope that clears it up!