According to VGChartz's front page hardware totals, PS4's market share is currently 57.1%.

However, in order to maintain/increase this percentage, it must outsell Switch and Xbox One combined; each week that it doesn't, its market share decreases.

Once PS4/Xbone/Switch reach their final numbers, do you think PS4 will still have a majority marketshare, or will it have fallen below 50%?

Nope. Switch is gen 9 though.

Not sure why you're including the Switch, but the PS4 should easily have 50% market share between itself/X1/Wii U as all 3 dedicate home consoles were released about a year apart.

It would not have a 50% market share if the 3Ds/Vita are included and the same can be said for the Switch.

Unlikely, as I'd say Switch will reach at minimum 80m sold and I can see X1 topping 55m. With the WiiU figured in that would mean ~150m for PS4 to maintain 50% and even if we take that out 135m+ seem a bit too steep a mountain to climb.

Not sure if the OP is talking about 2018 or generation 8.

If 2018, then the answer is definitely "no". If generation 8, then it needs to be compared to XB1 and Wii U. In this case, yeah it's going to stay above 50%.

LT PS4 vs Xbox and Switch, then no

Say the next generation begins 2020 and the PS4 does 130m and the X1 55m, then the Switch couldn't do more than 75m. I think it's more likely than not that the Switch surpasses the 3DS, though not by a large ammount, so likely not, unless its successor is coming no later than holidays 2022.

But... it'll do it up to the end of its time as the current Sony console. And also if you count the Wii-U instead of the Switch obviously.

In terms of 8th gen home consoles it has it on lock

No, Switch should be able to sell at least 70 million+.

However if it is against the X1 and Wii U then sure.

Okay my bad I should have clarified, I was looking at the marketshare as listed on VGChartz's hardware totals on the front page.