Are the turquoise and mustard the new additions or the old scheme, I'm unclear? What colour are the new walls, floor and curtains? And what's your home like- eg is it modern or old inside? A photo would be really useful OP, to see the room as it is?
You are on point with the velvet sofa which is still a really big trend and will probably last quite a few years. Navy is a great base colour, fashionable now but set to be in style for the next decade as sofas are longer term purchases. It's super practical and works with a bunch of other colours so that if you wanted to refresh your cushions and accessories regularly you could. Navy will also withstand entire wall colour repaints.
Millennial pink is very nice but it peaked in 2019 so I think you'd be risking it looking dated quite quickly. Grey was huge around 2017 but its past its peak so I think in a year or so you'd regret that. I would suggest going with jewel tones, certainly for furnishings, such as teal, emerald, dark magenta or plum etc. Alongside dark walls this looks great, or you can style with lighter base walls if you prefer. I would choose your chair in a jewel toned velvet.
As you mentioned you want luxury, one big trend at the moment for 2021 is Art Deco, and this works well with velvet and jewel tones. You can add accessories with gold, or glass elements, and include deco print cushions or rug. Plants also work nicely with this.
Alternatively if this is too luxe for you, then the Scandinavian trend has been updated to Scandi Noir - so the same emphasis on natural textures and clean lines but with less grey and a darker more luxe pallette. Eg teaming your navy velvet sofa with sheepskin, wood, wool, and dark or black accessories etc. This could work with a tan leather accent chair. Plants also look great with this.
I would choose your furniture in a classic style with feet, so that there is space underneath the sofa, chair, coffee table etc and it adds to the illusion of space.
Finally I tend to chop and change my cushions every season so that I get a nice refresh! I keep the old covers on underneath and change back when I'm bored! So you could have a summer and winter variation!
Good luck! Here are a few images of the above ideas - will post again below x