There are recurrent claims that "bitcoin adoption is increasing", but there seems to be few if any reliable numbers suporting the claim, and a few signs that it may not be true.
* The number of stores that "accept bitcoin" through Bitpay or similar service appears to be growing; but since the lowest ("starter") level of merchant registration in Bitpay is free (with a 1% fee on each payment), that number does not imply growing number of clients, or growing volume of payments. Moreover, it is hard to guess what percentage of the people who use Bitpay are "new adopters", or old adopters that buy more bitcoins specifically to use the service. It may be that most Bitpay clients are old adopters who use Bitpay to spend their old coins, since that payment method does not seem to have any advantage for the other two categories.
* Bitpay declared that they processed payments totalling 100 M USD in 2013. However it is not known how much of that is actual commercial payments (bitcoins changing owner in exchange for goods or services other than national currencies); as opposed to coins being bought or sold for investment and speculation.
* Blockchain traffic analysis shows subtantial transaction volume: about
100 kBTC/day =
60 M USD/day presently. However, the evolution of these numbers since January suggests that only a small fraction of that volume is actual commercial payments, the rest being investment/speculation or coins being moved between addresses belonging to the same person.
* The
number of new posts on bitcointalk.org had its peak in January 2014 and has then stagnated. A visual scan of the
recent posts page suggests that many of the new posts are now about altcoins. The number of registered members keeps increasing by 15'000 -- 20'000 per month, but there is no data on how many cease to be active. The number of
active members may well be stagnating or decreasing. The number of pages read per month keeps increasing, slowly, but that may be a consequence of the increased number of topics. In any case, a breakdown of these numbers by geographic country or region and by topic would be necessary to interpret them.