User Kornto from Xentax forum started development for *.rpf (rpf7) GTA V archive editor. This program is free and open source (published on googlecode), currently supports only viewing. For work you need the key.dat file with AES encryption key, which can be extracted from the Xbox360 executable file using the GTAVKeyExtractor or manually (if you are experienced in reverse engineering).
There are a lot of archives with the same format inside *.rpf. File export works correctly, some part of files is already available for research. For example, it is possible to open text files (*.gxt2), Ekey is working on the special tool.
There is no old *.ide/*.ipl, that formats are replaced with new alternatives. Some resource formats are well known: *.xtd/*.xdd/*.xft/*.xmt/*.xed (and RDR *.xsc scripts). Resource container structure is unknown yet (RSC7), research is in process. Everybody can participate, share info and help.
Also we can say that PC version of game can be considered as confirmed. Appropriate configuration files and resources are found in game archives.