This is not confirmed by SpaceX, but has been floating around the internet as the suspected reason.

Last year, SpaceX attempted a first stage water landing, but was not successful. Their two most recent successes on this front had at least two hardware differences from that old attempt: landing legs and heavier duty RCS thrusters. However, due to some combination of manufacturing and launch scheduling, an old core without these improvements, similar to their attempt last year, will be flying on flight 13.

Flight 13 will be a flight to ISS on a core without landing legs and other modifications for landing. Apparently, they swapped cores earlier, and now they have a rocket left without legs.

I believe it is because of this:

> However, our next couple launches are for very high velocity geostationary satellite missions, which don’t allow enough residual propellant for landing.

Based on the press release they plan on using Falcon Heavy for this type of launch in the future but it sounds like that project isn't ready for primetime yet.

I took that statement to mean they can't even attempt a landing on the next couple of launches because there will not be enough residual propellant for landing.

And then the next statement, I assume, refers to the next launches where they can attempt a landing.

EDIT: my assumption is confirmed here http://en.wikipedia.org/wiki/List_of_Falcon_9_launches

Next up are flights 11 and 12, which can't be landed.

Then 13 has the "low probability of success".

Funny that you cite Wikipedia, which is citing... the link that this HN discussion points to.

Yeah, I actually made that particular edit to Wikipedia about 20 minutes before seeing it cited as a _verification_ of that article, here. Funny to see one of those infamous internet self-confirmation loops get established in near-realtime...

Might be the flight path or payload limitations.

probably because it's another water landing

The last 2 water landings have been successful.