Tenants want to stay, but new tenants already paid deposit.

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In Portland, we must give 90 days notice to change rent/terms or renew lease. Tenants' lease ends May 31. 

March 1, I offered to renew lease for June 1, no rent increase. March 30, they emailed that they didn't want to renew the lease. 

I marketed the unit and screened/accepted new tenants, accepted holding deposit in secured funds. Agreement signing scheduled for next week, June 1 move-in.

Today April 11, current tenants changed their mind and say they want to stay. 

I told them I've already got a new tenant lined up and they can't stay. Their lease says they must inform me 60 days in advance if they want to move out or renew, and they already said they wouldn't renew.

The question is, do they have any legal grounds to stay? In Portland you must renew a lease otherwise pay tenants a $4,500 relo fee.  I offered to renew, but they declined. I want to make sure I can keep my agreement with my new tenants that they can move in June 1. 

(I think once they started looking, they realized they had a screaming deal at $1836 for a 3 bedroom in 97217, and hadn't known how good they had it. My new tenants will pay $1995, and even that is a good deal. It rented with a week of listing, sight unseen.)