If this is because your infra can't scale fast enough to support the new users coming in: Congrats! Thats an awesome achievement and a great problem to have. 

If this is because you are afraid of losing people's funds: We hear you. Thanks for letting us know and force the issue before it happens. 

If this is to prepare for a business model where alby is a paid Wallet, this is a great way to go. 

If this is just a marketing play to create a false sense of exclusivity, it's not going to work.