Let me rephrase the Angels situation
They currently have the lease through 2029.
There is a window to make a new lease that expires at the end of 2019.
Right now, there is nowhere for the team to move to, and the MLB basically won't approve a move, as having two LA area teams is important to its TV rights, both in North America and Internationally.
Of course, the window could be expanded if both sides agree.
The Angels want a new Stadium, or at least the current stadium upgraded. To make that happen, the team wants to develop the parking lot area to get enough money to build the new Stadium, similar to the recent Anaheim Ducks deal.
If a deal can't be made, then the Angels will play in the current stadium through 2029 while it explores other places to play, somewhere where they can promise a new Stadium for the 2030 season.
And then the city can look for alternative uses for the Stadium land. Maybe a developer that will build a large mixed use complex of retail, restaurants and housing, or maybe Disney would look into making an offer a decade from now.
But both the Mayor and the Angels know a deal has to be done this year, for many reasons, including scoring political points.
But if the Angels don't say they are not returning in 2020 by December 31st, the current lease is not breakable, due to major penalties if they do. So 10 more years of the team, or longer if a new deal is made.