To upgrade or not to do it it all depends of your photography style.. idont think that somebody that shoots just during the day might need High ISO.. or somebody that never do burst shoot might need it.. or HDR.. or if never use it under the rain or dust.. so it all depends.. whenever you fill that there is another body that CAN do it better than the one that you have and you NEED it.. so.. then is good chance to change.
Compare a K10D with a K5iis ( or similar ) is something like comparing an old 80s car with a brand new 2015, both are just just in different categories... but for some people the old 80s car could be enough for the kind of ride that they do, and perhaps dont really need electric windows, ac, gps, etc, etc ..
K5iis is a great great great camera and you wont be disappointed with it.