There is always the possibility that a tie would be impossible in 2016. If Puerto Rico were admitted as a state, it would get 5 Representatives and 7 EV based on the 2010 Census if no other state were to lose Representatives as a result of Puerto Rico's admission.
Could always have a third party candidate getting a few electoral votes.....or a Ron Paul supporting faithless elector turning a close election into a tie.
In which case, that third candidate would be among those Congress could choose for President. However, with Puerto Rican admission a two candidate tie would be essentially impossible unless an elector refused to cast a vote.
Not that I think Puerto Rico would be a State by 2016. The earliest date I see Puerto Rico becoming a State is 4 July 2017. That would follow a 2014 referendum on a simple statehood or the current status and then a 2016 referendum to adopt a State constitution followed by the 115th Congress accepting said constitution and admitting Puerto Rico.
