I just ran through the texts that I have available.
Jacob De Gheyn's Exercise of Arms Section III (Pikeman) Plate 14 “Porte your Pike (3rd Motion)” shows left foot forward right foot back. Any gathering would have to be by the right foot. This is a Dutch manuscript from 1607 which unfortunately does not give directions on the actual attacks. I can't find an online picture of the pike guards form De Gheyn
Joachim Meyer's 1570 text (Translated by Jeffery Forgeng) has a Part about combat with the quarterstaff, halberd and pike. In the guards for quarterstaff / halberd Meyer states they can be done on either side. In the German tradition for two handed weapons like a long sword the weapon at guard stays on the inside of the body, never passing to the 'outside'. For example in the plow with the left foot forward the pommel of the sword is set near the right hip and the sword tip pointed at the opponent's face. With the right foot forward the pommel rests near the left hip. For a guard to be done on either side, it is done with either the left or right foot forward. All of the pike guards are described exclusively with the left leg forward. Here is Meyer's description of a high thrust, like from a Ported pike:
3.40r.1 (Forgeng Translation):
“Hold your pike in the High Guard on your left shoulder, as I have taught; give your pike a covert swing forward, and meanwhile step forward with your left foot; with this step forward, thrust before you in at his face while your pike is flying upward in this swing, so that at the end of the thrust your arms are extended to the furthest; then as your pike drops back to the ground, you shall step yet further forth with your left foot, and pull your pike back to you with both hands before it has entirely fallen to the ground, lowering your upper body after the pike; and with this let it sink into the Low Guard upon the knee (which will be flexed well forward), such that the tip stands at your opponent's face.”
There are some thrusts that are done where there is a step, reaching thrusts where the left hand releases the staff. For the 22 Pike figures in the woodcuts, 14 are left foot forward. 4 are definitively right foot forward and one is possibly right foot forward. Of the four definitive right forwards, three appear to be passing step thrusts and one a retreat out of range of a passing step thrust. In there are two additional woodcut figures that are in right foot forward and in guard stances, but these are in the title page front plate of the book.
I should note that the Meyer is dealing with dueling and sport fencing, this is one on one pike combat but the basics should still hold.
A quick look at my Osprey Pavia 1525:
pg 16 Battle of Fornovo wood cut 1495 - Swiss Pike block is holding pikes in the middle of the pike with right leg/hand forward (pike on the left side of the body). The rear Glieder intrestingly is Niderstellton the right side.
pg 17 Seige of Alesia 1533 painting Landsknecht left leg / hand forward.
pg 37 Battle of Pavia by Hans Schaufelein 1526 Landsknechts - only two Spießträger are distinct. Both are right forward. - Gloss criticizes the work as a whole as inaccurate.
pg 39 Infantry Battle 1530 by Holbein the Younger - type unknown - Only distinct pike usage are three on the left of the picture all, are left forward.
The Renaissance at War - Thomas Arnold
pg 170 Francis's Tomb at St Denis - Swiss at Marignano 1515 - Swiss Pike in right/right while holding the middle pike.