Why is Arc+Sub out of stock until October, but Arc or Sub are in stock?

Maybe packaging? If the bundle comes in its own special box then that would explain it.

They don’t want us to apply 30% trade up discount code on bundle as code just works on one item only. So if we buy arc and sub separate it applies only on arc as higher price item and sub no discount. 

And where is your proof of this accusation? 

You can try it yourself if you have discount code. 

Code works on the bundle.  As of this post, bundle ship date is 10/23 , Arc only is  10/16, Sub only is 10/23.  Not sure where OP got his/her information from, but clearly bundle can’t ship till sub is available.   Although, it wouldn’t surprise me too much if Sonos split the order and shipped Arc and Sub separately when one or the other gets to the warehouse.

Implying that Sonos is manipulating shipping dates in order to minimize use of trade in credits doesn’t make a lot of sense.  They could have justifiably made trade credits apply to single items, no bundles, if they wanted to.

Not what I meant.  I was asking for proof that they don’t want us to use the discount on a bundle, because I know for a fact that is 100% untrue.  The discount can be used on any bundle except the ones that have 3rd party speakers or turntables.  Matter of fact, more than a few posters have gotten an entire home theater bundle, Beam/Arc, Ones and Sub with 30% off.  The bundle just needs to be in stock.  

Actually I think this has nothing todo with the later ship date and more todo with there 45 day guarantee.

if your buying the bundle your intent is to use it together as one system. So for example if so I ships you your sub 10/01 and you received your arc on 11/01 and you decide 12/01 you don't want Sonos, your already past the 45 days on the sub. So it just makes it complicated. Sonos also seems reflects the ship date of the last out of stock item.

in my case I ordered last Friday full bundle 30% off code, in white. My ship date is 10/16, but at the time that was the ship date for the arc and the sub. 
 

I also think these items are literally being sold directly off the assembly line, that's why we're getting these far out dates, to cover shipping time from the factory etc. the dates are pushing out so far as they can't keep up with demand due to restraints of covid. 

I wouldn’t think that would be that big of an issue.  They couldn’t really start the clock on the return until you received the whole bundle.  I also wouldn’t think shipping cost would be a problem as it likely costs the same to ship separately as it does together (I don’t think there’s a bundle box).  However, Sonos doesn’t charge your credit card until they ship the product, and they can’t charge you for the whole bundle till they ship the whole bundle.  Shipping a Sub, for example, without charging you would be a bad idea, since your card could be invalid by the time the Arc ships.

Yep.  It’s also why a lot of people are actually getting their product shipped much earlier than the stated shipping dating.  A lot of uncertainty in getting the products made and shipped to their warehouses before they ship to you.  Better to overestimate and get it out early rather than ship late. 

Latest cinema packages are now saying discontinued rather than out of stock now. Anyone know what’s going ok?

On the Sonos site?  I am not seeing discontinued on the US site.