I think the companies knew that multiple contracts were an option, but judging from the press coverage in the week or two leading up to it, the business pundits thought it would be the traditional multiple proposals, one winner option.
I don't know what will happen if both deliver a fully functional vehicle by 2017 within the budget. We still could be in the Y stage of the process, e.g. the YF-22 and YF-23 fighter technology demonstrators which were functional aircraft leading to the choice of the YF-22 to go into production as the F-22.
NASA could also go head post-2017 with both companies supplying vehicles and launches. We'll have to see.