[Update: for the impact factors released in June 2016 read the new blog post]
Thomson Reuters has recently released the 2015 edition of the Journal Citation Reports, a publication that contains the impact factors of journals they index.
I have compared the new impact factors to the previous ones (from the 2014 edition of JCR) for several GIS journals indexed in Web of Science. The result is shown below. Both the relative and absolute IF change are included.
It’s interesting to see that almost all GIS journals have seen the increase of their impact factor, some of them considerably: Cartography and Geographic Information Science has almost doubled it!
ISPRS International Journal of Geo-Information is the newest addition to Web of Science, but it is too recent to have an impact factor. According to the editors of the journal, the JCR that will be published in July 2016 will contain the IF for IJGI.
Please note that this is my personal list of indexed GIS journals, and it may differ from your preferences. For a more comprehensive list please see the internal list of my group.