Even as a amateur part time puzzle solver who will never get any where near WR times, I will give my opinion on these claims.
1. There are less and less cubers on competitions worldwide,
2. There are less and less speedcubing video blogers,
3. All records are at (or close to) maximum possible,
4. All cubes are already designed perfectly (or close to),
5. Speedcubing will never get more popularity then what it has now...
1. False.
2. False.
Even though some older and famous video bloggers have left the scene, people are taking their place in an ever increasing amounts.
I have watched hundreds of cubing / puzzle videos on Youtube since May 2009. My favourite is "Crazybadcuber".
3. False.
Unofficial WR's are lower than official WR's.
People have got 4.5 seconds on a 3x3x3 cube and 22 seconds on a 4x4x4 cube.
4. False
Cube and puzzle technology is improving still!
5. False (but only as a non mainstream media covered event).
Claim 5 is true if you compare puzzle solving with the Rubik's cube craze of the early 1980's. I was there in 1980/1981 as a 10/11 year old
and in those years my parents brought me a Rubik's Cube to solve and even funded two solution books to help me solve it. Despite all that,
I could never solve a Rubik's Cube and gave up. In May 2009, I brought one of the books my parents got me in 1980/1 on Ebay and brought
a store brought cube to use. I found that I got the directions of D and D' wrong. Apart from that, I would of solved a 3x3x3 in 1981!
And since then I have solved a lot of puzzles, including many cuboids (ie 3x3x2, 3x3x4, 2x2x4, 2x3x4, etc) and cubes (from 2 to 9 layers and 11 layers).