Cinemark and others will almost certainly continue to pursue their own large format strategy but this thread on the Cinemark board points out one of the big barriers to them getting rich doing so.
Most believe that they want to have their own large format to avoid IMAX's cut of the take. The problem is that they will spend that cut and more getting the people into their XD Theaters.
Over the long term they COULD reach a critical mass that would justify advertising and promotion on a scale that would make it cost effective but that will most likely take a long time and require them to build their own brand (XD or whatever) from scratch.That takes time and money. In the short term they can only do this piece meal since their XD is only in select locations. Meanwhile IMAX is already a brand with global recognition that is prominently featured in the huge national and international ad campaigns by the studios. That's a big barrier for them to overcome.
I'm not so sure that makes sense if all they are trying to do is keep from giving IMAX a few bucks. I don't believe that is the primary driver in this.
The theater chains agreed to the JVs because there was a lot of uncertainty about whether IMAX in the multiplex and DMR would be a success. That is no longer a question. I think that the major chains will eventually shift over to the purchase/lease model for new screens and as the JVs expire to minimize IMAX's cut rather than trying to cut them out altogether. Especially if IMAX can continue to fill theaters and differentiate themselves with superior image quality, sound, and yes, big screens. I don't think every screen needs to be the size of the largest IMAX theaters but they should be very careful about assuming size doesn't matter.