It seems a "chimera" is a different thing from a "hybrid". The creatures are mostly pigs, with a tiny percentage of monkey cells. There is no mixture of pig and chimp DNA within each single cell, as would be the case with a hybrid animal. There's no way that this would propagate to another generation.
From the link:
In total, 4,000 embryos received an injection of monkey cells and were implanted in surrogate sows. The pigs bore 10 piglets as a result of the procedure, but only two of the offspring grew both pig and monkey cells. By scanning for spots of fluorescent green, the team found monkey cells scattered throughout multiple organs, including the heart, liver, spleen, lungs and skin.
In each organ, between one in 1,000 and one in 10,000 cells turned out to be a monkey cells — in other words, the interspecies chimeras were more than 99% pig.