ISTR that they would skip the 4 (unlucky?) and the next series would be the “5S”.
It would be inconsistent to change the primary chipset without changing the final digit.
I probably read it here, but:
The first number (1-2 digit) is the speed: 4, 8, 12, 16
The second number has been:
0 for single format (401S)
1 for dual format (many)
3 for DL support (many)
5 for “revised” (451S, 851S - dual, 1653S - DL)
The third is the chipset.
So we can predict that the next drive with a new chipset will be called:
SOHW-1615S (in dual format)
SOHW-1635S (or maybe 1655S) in DL - or they might shock us with a 6 or 7, if does get faster +/-RW as well
That it will do 16x on +R is a given (nobody will launch anything less)
It may well do 16x on -R as well - the competition are getting there NOW - 12x would be marked as a weakness.
It will have to do 4x on DL - if speeds aren’t pushed further
It may well bring in 8x on +RW, and perhaps 6x on -RW … it’s something they have to be aiming for