One clearly sees the steady rise of the pronunciation /pɔː/; around 80 per cent of those aged around 40 or younger indicated that they pronounce the word with a monophthong. However, nobody knows if the pendulum will swing back.
Most of my EFL students (who are in their twenties) use a diphthong in poor, which is probably due to the fact that their teachers at secondary school used or still use a diphthong. To present them with a 'younger' pronunciation model I changed my pronunciation from /ʊə/ to /ɔː/. Doesn't make me younger physically - alas!