Racking after six months

I've had this batch of stout aging for about six months.

It's in the secondary now and I'm going to rack it this weekend. I'm worried there won't be enough live yeast to carbonate it.

Should I be concerned, or just go for it?

You should be ok...one thing to do is when you start racking to your bottlign bucket, rub the bottom of your autosiphon or racking can back and forth across the bottom once to kick up some extra yeast sediment into the beer. Watch it flow into the line and bucket for about 30 seconds to a minute then lift it up a bit till it flows clean and hold it for a couple of minutes, then lightly lower it back down and let it continue racking. A little more yeast will come through, but in a couple seconds, the beer will form a clean runnel in the trub and flow clear for the rest of the racking.

When I've had doubts about the viability of the yeast, I've just added a little bit of dry yeast.

I boiled my priming solution, and cooled it, then added about 1/4 package of nottingham yeast and poured it into my bottling bucket. I had it sit a minute, and it got a little foamy, and then racked the beer into it. It worked out great, and I had good carbonation along with clear beer.

You could drag your racking cane through a bit, and that would work too. I was just worried about some trub and some yeast that may have autolyzed, so I added fresh.