Coming from a team that usually makes a goal out of capitalizing on auto (2006 shooting auto, 9 auto lines in 2008, 3-5 ball auto in 2010, two-tube auto in 2011, center or corner bridge auto in 2012, two-ball auto in 2014, 3-tote auto in 2015), we're very impressed with the difficulty of coordinating a multi-ball auto this year.
The obvious route; get a ball from the center line would be difficult without the mid-line rule... it becomes astonishingly difficult with it (I'm sure a literal handfull of teams will have one).
The secondary route (achieved four obvious ways) is probably less technically difficult, but requires coordination to get the extra balls from your partner(s)... and only helps if one or both of your partners can't score the ball high in auto (common early on, but some DCMP or CMP alliances may have three High Goal autos).
1. Spybot passes its ball to a HG shooter after it scores its first ball from the courtyard.
2. Spybot receives ball from a partner that passes ball, after the Spybot has shot its first ball.
3. Neutral Zone bot drives into Courtyard, scores, and then comes back for a partner to pass a second ball, then returns to Courtyard and shoots.
4. Neutral Zone bot drives into Courtyard and scores first ball, meanwhile partner(s) pass a second (and third?) ball to scoring bot, who must sequentially score those.
My gut is that these will also be very rare though, since they require partner coordination and may compromise other potential auto modes that would better prepare the alliance to 'hit the ground running' in teleop (such as preparing to defeat other defenses and/or gather the midline balls).
I suspect that an ordinary, reliable HG or LG auto will probably be about as rare (maybe somewhat less so?) as 2-ball autos were in 2014... it's non-trivial to defeat a Defense AND know where you are well enough (or use auto-targeting well enough) to make the shot reliably.