20-30 unless something happens.
Some people did something?
I concur with your estimate. I believe it'll be a region by region takeover.
These numbers are from 2011 (Birmingham is now 29% Muslim. I predict 35% is the tipping point - let's watch what occurs there over the next decade.):
The top 20 local authorities in England and Wales with the highest percent of Muslims in 2011[44] were:
London Borough of Tower Hamlets 34.5% 87,696
London Borough of Newham 32.0% 98,456
Blackburn with Darwen 27.4% 38,817
City of Bradford 24.7% 129,041
Luton 24.6% 49,991
London Borough of Redbridge 23.3% 64,999
Slough 23.3% 32,655
London Borough of Waltham Forest 21.9% 56,541
Birmingham 21.8% 234,411
Leicester 18.6% 61,440
London Borough of Brent 18.6% 58,036
City of Westminster 18.3% 40,073
Metropolitan Borough of Oldham 17.7% 39,879
Pendle 17.4% 15,579
London Borough of Enfield 16.7% 52,141
Manchester 15.8% 79,496
London Borough of Ealing 15.7% 53,198
Kirklees 14.5% 61,280
https://en.wikipedia.org/wiki/Islam_in_the_United_Kingdom
