There is no other model from CANON that can print A3 and is compatible with your "old" CLI571 ink cartridges.

Hi Megan
The iX Pixma 6850 requires the CLI551 and PGI550 ink series. The XL cartridge sizes are also compatible.

The MG6850 requires the CLI571 and PGI570 ink series. The XL cartridge size is also compatible.

I actually bought mine and put edible ink for pictures to put on cakes.

Hello...I think not. My iX6850 (I'm very satisfied, by the way - I work with pictures) has the number 550 and 551. The MG6850 has the number 571 :-(( Option: sell new ones at a lower price :-)
With best regards

The Canon IX6850 requires the following cartridges:
CLI-550PBK, CLI-551BK, 551C, 551M, 551G
The MG6850 requires the following:
PGI-570P, CLI-571 etc.

They are therefore not the same cartridges

There are many Canon printers that use the PGI-570P, CLI-571 cartridges, e.g. look here:
Canon Pixma MG5700
Canon Pixma MG5750
Canon Pixma MG5751
Canon Pixma MG5752
Canon Pixma MG5753
Canon Pixma MG6800
Canon Pixma MG6850
Canon Pixma MG6851
Canon Pixma MG6852
Canon Pixma MG6853
Canon Pixma MG7700
Canon Pixma MG7750
Canon Pixma MG7751
Canon Pixma MG7752
Canon Pixma MG7753
Canon Pixma TS5000
Canon Pixma TS5050
Canon Pixma TS5051
Canon Pixma TS5053
Canon Pixma TS5055
Canon Pixma TS6000
Canon Pixma TS6050
Canon Pixma TS6051
Canon Pixma TS6052
Canon Pixma TS8000
Canon Pixma TS8050
Canon Pixma TS8051
Canon Pixma TS8052
Canon Pixma TS8053
Canon Pixma TS9050
Canon Pixma TS9055