End up, the plan changed. I didn't shift everything on the same day. I shift my old tank aside and run the new tank concurrently. About a month then I shift everything over. But it shouldn't be a problem even if you transfer everything in a day if you are reusing rocks from the previous tank.
The only problem is that it will be quite a bit of work, depending on how big is your previous setup is, you need to have enough containers to hold the livestocks for a few hours (temperature can be a concern) while you prep for the new tank. You will need time to setup the new tank, prepare the water and aquascape etc. If you can hire someone professional to do it will be good or best run both tanks concurrently den slowly transfer over.
The another issue is whether you will be reusing the sand from the old tank if you have sand or planning to have sand in a new tank. I dont really recommend reusing the sand from the previous setup, as when I scoop out the sand from the old tank, it is full of detritus and bristleworms. Unless you can wash them really clean. I used new sand instead and prefer to wash them with ro water before using to avoid any unnecessary aglae or mini cycle.
If you are adding new dry rocks, I feel it is better to cycle them in a bucket in advance and dose bacteria etc or like what other reefers mentioned, put them in your sump. It helps to establish your new tank faster and avoid any unwanted algae. After running the new tank for about six months, through these period, I have algae blooms on the new dry rocks but not the old rocks. Now, it starts to settle down already and coraline algae is slowly taking over. No matter what, the new tank will still take some time to settle down and establish but probably not as bad as a brand new tank. If you are reusing the rocks and biomedia from the previous tank, the biofiltration is there. You can just dose some bacteria to help seed the new sand and rocks. The bacteria population is dependent on the bioload. These are some of things I encounter.
I'm not an expert. More reefers can help to chip in and correct me if I'm wrong :).