I've actually found that 26" wheels are more fun on pavement and 700c feels better in the dirt....a complete turnaround from the orthodoxy 20 years ago!! I'm keen to try 650B/27.5 wheels but can't justify the expense right now. I'd love to try 27.5 off-road and I'd really love to convert my 700c street bike to 650B.

Expedition touring/bike camping is really taking off right now and companies like Surly (LHT), Rodriguez (UTB) and Co-Motion (Pangea) are putting out some fantastic 26" wheel bikes that are specifically designed for this activity (Surly a bit less than the other two but the LHT is still capable). This might be the saving grace for high quality 26" wheels and tires no disappearing completely.