It's not worth it selling out and using rental, you will literally just lose money. Unless you want to try different decks every week.
It will probably take a lot of time until arena end up having all the cards pool. And I don't think they will shut down mtgo until there. They know there are A LOT of people that play different formats than standard and limited that would rather play anything else than waste time playing standard. I don't think arena needs the player base from mtgo. And honestly I think the 'profit per capita' of mtgo is bigger than arena's.