You do realize you can still count up to 5 with your fingers even if we used a different numeral system? So you would signal in the exact same way that you do now. Or you know, just shout or something? How often do you need to signal a small number from a distance?
Actually you can count to 12 quite neatly on one hand. Simply take your thumb and place it on the bottom segment of your little finger. Excluding your thumb, you have 12 segments on your fingers.
As you count, move your thumb up one segment, switching to the next finger when you reach the top. This way you can count to 12 on one hand.
12 has more prime factors than 10. 12 has 2, 3, 4 and 6. 10 only has 2 and 5. This also means that thirds and quarters are much easier to do everyday maths on and those fractions are much more common than fifths.
For example, in base 10, a third is 0.33333..., going infinitely. But in base 12, a third is just 0.4. The times table for 2, 3, 4 and 6 is also much easier.
Tau makes much more sense than pi because it is based on the radius of the circle rather than the diameter. The radius is the more fundamental property of the circle. You'll actually see 2pi appear in many formulas. See also https://tauday.com/tau-manifesto
Anyone who claims to know the answer is either delusional or deliberately lying. Nobody really knows what the future holds.