Those that continue on 2013 must have parallel focus or be hit like Ferrari and McLaren in 2008-9. McLaren pushed so hard for the 2008 title that their car in 2009 stank for half the season and they basically redid the 2009 car after the first few races.
Caterham ->2014 since late 2012, now half half development it looks like.
FI – Should change to 2014 now and just try and make 2013 car work on the old tyres/circuit tweaks
Same for Ferrari, Marussia, Toro Rosso,
I have a feeling RBR, Lotus, Merc, McLaren, Ferrari will all try and continue 2013 to late alongside a growing 2014 project, they have enough people to do that, same with Ferrari (Byrne/Allison focussed on 2014 project). Sauber and Williams should make sure their 2014 cars don’t bomb like their 2013 revisions, same with McLaren.