That's operating under the assumption that other teams are latent. Bangladesh may improve, but so will others.
Actually I expect most countries to go backwards. That's what happens when finances and popularity declines. It takes 20 years to show on the field. Bangladesh background situation has been improving for ten years, but it is only now that the ones who had better coaching and exposure since they were little kids are becoming old enough to play for the nation.
Players like Mushfiqur said they had to learn everything at international level with no domestic structure, no exposure and no great training when he was a kid. Their current crop of youngsters like Liton Das, Soumya Sarkar have had much more exposure and played multiple U-19 cups and been coached better.
People don't realize that the gap between South Africa and Bangladesh is just one or two special players. Don't believe me? Imagine AB and Amla were Bangladeshi. Do you think SA minus AB and Amla would beat a Bangladesh side that read Tamim, Amla, Soumya Sarkar, AB, Shakib, Mushfiqur, Mahmudullah? SA would suddenly read De Kock, Roussouw, Faf, Duminy, Miller, Parnell.
Seriously, which of those lineups do you think is better? Is there even a debate?
Even a side like Afghanistan or Ireland could look World Class with two or three elite players. There just isn't much quality difference between the average players on most sides, it's the top 3 or 4 players that generate the quality.
If you agree with what I wrote till now, consider this. In 10 years, AB, Amla, JP, Morne, Steyn will all be gone. Their replacements are the kids who are getting clobbered by Bangladesh U-19s....and those Bangladeshi kids will be the ones replacing the older Bangladeshi players (who are noticeably the weakest players in the BD side). I'm not making that up earlier. The biggest failures for Bangladesh were Tamim, Mashrafe and Imrul whereas SA's strongest players are AB, Morne, Amla, Duminy, Steyn, who will only last another 3 or 4 years.
Look at the pipeline, because that's where the truth will come out. Sure, Australia will be fine for years to come. England is low in the talent department and interest is plummeting. WI is in freefall. Pakistan and SL have huge administration and corruption issues. NZ is a tiny country which got Bangla-washed 3 years ago and interest in cricket was dropping until this WC.
Structure matters. You can't just look at the current top 11 and make a prediction because these guys won't be playing in 10 years.