He won't end the year as #1 unless he starts owning Djokovic, but he can definitely end the year #2. Definitely.
To do that he should have outperformed Nadal and Federer on his best surface, i.e. slow hard courts - he's sure as hell not going to outperform Nadal on clay (and probably not on grass). Yet he came out of Aus Open/IW/Miami will fewer points than Rafa and Roger.
He needs to focus on his strengths and play the right calendar to maximise points. Nadal for example focuses most on the IW-US Open swing - particularly clay courts - as he knows he needs to peak then. Fed knows that indoor is now his domain so he wisely skipped Shanghai etc. to gear up for his indoor assault.
Murray will have to do spectacularly post Wimbledon i.e. US hardcourts, Asia and indoor to overtake both Nadal and Federer for the year end no.2
Then again, all it takes is him winning Wimbledon and the US Open, whilst Nadal wins RG i.e. he will have 2 slams to Rafa and Novak's 1 and suddenly even the no.1 could be in sight with some US hardcourt masters added on.. Think the race this year will be tight and Murray's attitude is the right one - if you don't believe in yourself, why should anyone else....