Should i wait for new RP before applying for my spouse's visa

I have been working/living in Belgium since 4 months and have my RP due to expire in Mar 2020 (WP due to expire in Dec 2019). I have already applied for Single permit extension and expect to receive it by Dec 2019 end.

I want to immediately apply for my spouse's visa(within oct 2019/nov2019)- because the duration of processing will be less if applied within 6 months of travel.  But have this doubt that he will get very short visa because my WP is about to expire.

Can someone help me in understanding what the best way out for me in this. Thanks in advance !

Apply for his visa, and while it is in processing when you get your WP renewed, send a copy of that to the processing agency. And also, duration of D visa really doesnt matter, because he needs to convert that to a residence permit once he is here.

Many thanks for response Aneesh, however i have one more doubt, my RP has old address and i can apply for update in address only by 24 Oct 2019, the address update process usually takes 3-4weeks (i heard). But if i submit for my husband's visa by Oct end (while RP address update is still in progress).

Is it okay ?

I ask this on assumption that they will not validate RP and corresponding address immediately. Thanks already !

Correct. And do mention this in the cover lettter. Once the new address  is registered, send that info to the processing office.