Dual Citizenship

I thought under the new scheme, we could not apply for citizenship for 10 years? (ILR after 5)

No, where did you hear that?

It could be 10 years for some people but that's only in certain circumstances (like they've overstayed a visa)

For citizenship, if you are married to a UK citizen, you just need to:
- hold ILR
And
-have been resident in the UK for the last 3 years

If you are not married to a UK citizen, you need to:
- have held ILR for 12 months
And
- have been resident in the UK for the last 5 years

I am certainly glad that my husband won't need to give up his UK citizenship as well. It's just nice to have the availability.

Don't you like your husband? Is there any particular reason you wish to see him suffer?   

Seriously, you are in an enviable position for now with your husband being an NRA for US purposes. He is able to invest in the UK, receive benefits, buy a house and have a mortgage without complications, and on and on. As long as you wish to remain in the UK, don't let your husband have anything to do with the US. That includes making sure you file your US tax return as 'married separate'.

If at a later point, you both wish to move to the US, then your circumstances will be different. But, bear in mind if you ever wish to eventually return to the UK (would your husband wish to spend the remainder of his life in the US?) he will want to only have a 'short term' green card. If he were to be a long term permanent resident of the US or acquire US citizenship, returning to the UK in the future would come with downsides.

US citizenship for your husband only if you both wish to remain in the US for the rest of your lives.

On the other hand, if you wish to acquire UK citizenship, currently, there are no downsides regardless of where you live. You already have the US taint, and that will continue forever unless you renounce.

I was under the impression that  I can declare citizenship after 5 years here in the uk,

You can't declare citizenship, you can apply for citizenship to be granted, but it's not a right. That's why a refusal of British citizenship cannot be appealed and even if granted, it can be removed.  The UK immigration rules end at ILR. British citizenship has different rules.

And some other countries don't allow dual citizenship (Germany for example).

Germany has exceptions. I know a US/German (USC born) dual citizen and three Canadian/German (two German born, one Canada born) dual citizens.

Germany has exceptions. I know a US/German (USC born) dual citizen and three Canadian/German (two German born, one Canada born) dual citizens.

Very cool!  I didn't realise that.   

Very cool!  I didn't realise that.   

As I understand it, Germany also has instituted a special rule for USCs. As was mentioned, there are now exceptions, but many acquiring Germen citizenship still must renounce any prior non-German citizenship. For USCs, due to the exceptionally high cost of US renunciation, if the amount of the US renunciation fee is over a certain percentage of their income, they do not have to renounce USC.

Question; if my 3 kids (USC and born in US) with UKC dad (born in UK) now have both passports & dual citizenship, do they ever have to give one up in their lifetime or do they just keep renewing passports and will always have it?

Question; if my 3 kids (USC and born in US) with UKC dad (born in UK) now have both passports & dual citizenship, do they ever have to give one up in their lifetime or do they just keep renewing passports and will always have it?

Nope, they will always have both UK and US citizenship, unless they consciously choose to renounce one of them when they are older.

Question; if my 3 kids (USC and born in US) with UKC dad (born in UK) now have both passports & dual citizenship, do they ever have to give one up in their lifetime or do they just keep renewing passports and will always have it?

You don't have to renew the passports either. You don't need a passport to be a citizen but, you need to be a citizen to have a passport.