One of the changes that I have noticed in the last year is that some of the operators who have been opposed to WiFi in the past have not only embraced it but are now trying to monopolise the same WiFi spectrum they billed as interference prone. Personally, I think the future of Wi-Fi is not just offloading but also working together with LTE. We are billing this as 4.5G and have recently produced a whitepaper, available here.
There has been a flurry of activity on Voice over Wi-Fi in the last few months. Recently the UK operators '3' and EE announced that they are both allowing WiFi calling and SMS. While '3' customers will have to use an OTT app for the time being, EE customers will experience this seamlessly.
I heard Taqua in the recent LTE World Summit talking about their solution and have offered to share their slides (embedded below). It was interesting to find out while having a discussion with them that their solution supports 'hand-in' and 'hand-out'. This takes away a major advantage that Small Cells offered, seamless roaming. Anyway, feel free to let me know of you have any opinion on this topic