I think being illiterate played a big part in what you describe above. As more and more apnay become literate, and more and more Sikh texts become accessible, coupled with the fact that being in a diaspora seems to inevitably result in some sections of the diaspora to focus on and try and understand and reflect upon their heritage and preserve it, we will see a renaissance of sorts. This will feed back to the people back home in time.
As an example we've been alienated from Dasam Granth for a long while so a rising awareness there alone will change us. Cultural practices like jathera will also diminish over generations due to simply losing the connection to your village and it being irrelevant. Many will lose that casteist sense that restricts marriage between Sikhs of different castes. The dynamics of the community will change - and it doesn't have to be for the worse, it can be for the better.
I do honestly believe we have a rich and powerful heritage. Someone on SA articulated it perfectly for me a while back. It's like various metals that have been underground since the beginning of earth, only to lay there untouched/unused, as time progressed man became aware of them and started to use and understand them more and more - from basic tools/weapons, to modern sophisticated industrial uses of today. Sikhi is the same. We haven't caught up with it yet - partly due to our own baggage and backwardness and partly because external forces have been trying to manipulate and exploit it for their own purposes.