It looks as though this guy has secured the Manor drive though it hasn't been officially announced yet.
So who is he? He's an Indonesian race driver aged 23. He's had a lot of single seater experience. For the last four years he's raced in GP2 for different teams with mediocre results ( 14th 19th 15th) until last year 2015, when he raced for Campos and finished 4th. And that was quite a string field.
In 2014 when he finished 14the he was partnered with Rossi, but comparing results is difficult because they didn't race against each other all season, there were team changes.
Prior to his GP2 career, he raced in GO3 in 2010 he raced for Manor and finished5th , he was also F1 test driver that year.
And in 2011 he raced for Marussia Manor and finishe 7th...he also seemed to be racing in other series that year.
So that's the guy who looks likely to partner Werhlein.