I highly doubt there's gonna be any if maybe only a few 3DS games that are going to be 8GB, maybe New 3DS exclusives but even Xenoblade Chronicles I'm predicting is likely going to only be 4GB but a minimum of 8GB Micro SD is recommended.
If you're going big why not get a 128GB Micro SD that is the biggest they come ATM, next year we might see 256GB Micro SD's with the likely of current 128GB Micro SD's dropping in price.