The prices wont be the same again ever. Since most of the new and mid tier players have GRs/Devis/anegling/Myst from the event too. Its much like everyone has a GR now and there will not be a buyer. The prices will rise slightly if around 100-200 of such MVP cards are bought by players after event. Unless you get a huge exodus of new players - Prices are going to stay between 3-7M for these 4 cards.
yeah price will never be the same again, but its good for newcomer and mid tier player to catch up.
Think about this: Number of OCA earned per day * number of player doing the event * 21 days
so approximately = 150 * 100 * 21 = 315,000 OCAs once this event is over.
How long it gna takes to get back = never