In February, Rio Tinto said it would spend a further $20 million...

In February, Rio Tinto said it would spend a further $20 million on studies to examine the Jadar deposit in Serbia, where it had invested $70 million to-date and which Rio Tinto estimates could account for up to 20% of annual global lithium supplies if mined.

Rio Tinto lithium resource in Serbia (125.3 Mt grading 1.8% Li2O) surpasses the one owned by Pilbara Minerals Ltd. at Pilgangoora (80.2 Mt grading 1.26% Li2O).

^{- http://www.marketwatch.com/story/rio-tinto-excited-by-serbian-lithium-project-2016-06-01}

I reckon that any junior lithium company that is not able to place their product on the market by the end of 2017, will have a hard time hoping for favorable market conditions that would fuel their further development.