As we all know, mobiles are everywhere and are probably used a lot more than desk phones and soft-phones so it's going to be the implementation of SIP into these devices that really makes the SIP revolution take off. Some expected numbers are detailed in the post on the Comms Dealer UK site that predicts 435 million sip users on mobile devices by 2012. Of course the adaptation of SIP and SIP services within developing IMS systems will be important as well as mobile device manufacturers realizing that it's not fair shipping devices with the SIP functionality disabled. People will want to use their phone over the GSM and 3G networks but also Wi-Fi networks 'seamlessly' (when a hotspot is available) and still be able to call people from their contacts list easily without having to use separate client software loads on their mobile - i.e. having to load Skype. Again, all interesting stuff and another reason to get trained on SIP as it's here to stay and for a very long time!