I've just had a look at VLM 2012 results to see how many men/women age 50+ ran sub 3. There were 69 men (55 of those age 50-54) but in the women there was only 1 and only 15 between the ages of 40 - 49!
Minni, I think that there is a big distinction between running sub 3 at 50 and running sub 3 for the first time aged 50. On the runbritain rankings there are 94 V50 with sub-3 performances in 2012 but a lot of them have faster times from younger days.
Finding those with no previous marathon experience who broke sub 3 at VLM 2012 shows:
Fred Zalokar 2:37:35 age 51 first timer according to po10 but well known masters runner form USA http://www.all-athletics.com/node/446454
but behind him a lot of impressive runs and PBs but a lot have previous with sub3.
Fastest I find is Colin Ridley: 2:53:50 after 3:00:22 in 2010. This guy sort of fits into the classic mould of middle distance going long in his later years so he is fit but does not have the tiredness in his legs of lots of years running long.
I am told that a minute a year is expected drop off when the drop off starts, so most V40 who can run sub 2:50 can sub 3 at V50. I am 47 and almost 2:50 so am looking to be well within 3:00:00 at VLM 2016.