When you order from Dell, they are able to tell you before you order what the drive will be. There is usually a number on the order line for the disks that you can drop into Google and see what it is.
Dell sell vSAN ready nodes and there are a large variety of disks that will be the same or very close to the spec that you need so I would firstly look through the HCL to see what specs that are not EOL will work for you. I would be surprised if you couldn't find any Dell 1.6TB 10k SAS disks that are not EOL. Even if they are EOL, look at the warranty that Dell will offer you.
For replacements, you need to explain that the disks are used in vSAN and you need the model number of the new drive to check the HCL and to ensure correct firmware is available etc. Support are able to do this for you, just explain the situation and they will work with you for a replacement. It's easier if they are vSAN Ready Nodes but the same thing applies.
In terms of non-Dell drives, I would not recommend it, you will probably want the hardware support from Dell.
Hope this helps?