To get a mine in production you need grade, tonnage and location, as well as a decent price of your products.

For NOT the nickel grade(plus other valuables) is more or less proven.

Tonnage is still lacking. For nickel laterite ores, the minimum tonnage is in the range of 30 to 40 million tonnes for operating mines, and go as high as more than 200 million tonnes at grades of about 1.5% Ni or more. You just don't spend huge infrastructure money on a mine that lasts only a couple of years. I guess that annual ore processing should for the sake of scale of economy be at least 3 million tonnes per year.

Location I am not sure about. Land shipment is very expensive compared to bulk ocean transport. Loading and unloading also cost money. Voisey's Bay is good since the ore body is very close to a good ocean harbour. You also need to build a huge tailings dam for the rejects from the concentrator. The ground and topography should be ok for that purpose. Power, roads, rail may also be very expensive. Shipment of your nickel concentrate(about 10-20% Ni depending on the mill and the ore mineralogy) also is a big issue. Lots of heavy trucks on the roads

Furute price of nickel, copper, pgm's etc are uncertain and depends mainly on the growth of the world economy. No large mining company will use the present(and very high) prices in their economic evaluations of future projects that may come on stream in 10 years or so. They will look at the past and try to use a fairly concervative price prediction.

These are just my personal opinions and carry no weight