Although there were some reports suggesting that reigning F2 champion Andy Soucek could replace Heidfeld in that position within the Brackley based team – having already terminated his deal with Virgin Racing – Germany's Auto Motor und Sport begs to differ. According to the aforementioned publication, Mercedes GP did not yet agree to appoint a regular reserve driver for the remainder of the 2010 season.
Under the current FIA regulations, the teams are not obliged to appoint a regular test/reserve driver during an F1 season. However, each team has to field 2 drivers at every event – there are 7 races remaining in the 2010 campaign.
It's therefore likely that Mercedes will go on in 2010 with no permanent reserve driver, choosing to appoint a racer in that position on a race-to-race basis. A 3rd driver is needed in the garage at each grand prix at least for precautionary reasons, in case one of the existing race drivers fails to make it to the grid.
If the reports turn out to be true, this means Mercedes GP will use its existing race drivers to help develop the 2011 car. As confirmed by both Michael Schumacher and Nico Rosberg in recent weeks, Ross Brawn's squad has turned its focus to the next year car, as the ongoing campaign doesn't have anything more to offer to the German-British team.
Having an experienced driver like Nick Heidfeld develop the 2011 car would have been great for Mercedes GP – the German has started 167 grands prix in his F1 career – but that's no longer an option, so Schumacher's and Rosberg's development roles will probably extend to the 2011 campaign also for the remainder of the year.