You're absolutely right, I forgot that lead in - I thought it had already started. I think that deferring the pension at aged 65+ is probably a risk too far. The increase is minuscule whereas you can do something worthwhile with the cash for that extra year or so in the meantime. What would I consider doing?
If I didn't need it, and I'm assuming that if I'm considering deferring it, I don't, I'd consider taking it. I'd then consider chucking it into a cheap as chips personal pension (if I had relevant UK earnings to justify it), getting a minimum of 20% tax relief (up to £3600 gross for even a non UK tax payer) and (hopefully) getting some investment growth on top of that.
Then, as someone with a defined benefit pension of the size that most of us have, I'd consider the pros and cons of taking it with practically no controls (tax free cash and the balance drawn at marginal rate or kept and bequeathed if it isn't needed).
You could (conceivably - nothing guaranteed) invest in cash funds and still beat the 5.8%. If I died before aged 75 (from April 6 onwards), it would be left to my partner or the local dog's home free of tax and not lost to George Osborne. If I died after aged 75 it gets taxed. Best I spend it then!