More accurately, based on Nokia's naming convention, the Lumia 930 is the successor of the Lumia 920, if that much isn't obvious. The 930 is the "full-featured, high-end smartphone" of Nokia, as with all 9XX models (like the 920 and its variants the 925 and 928, and the older Lumia 900 running Windows 7.8). The 8XX (820, 822, 800) are the medium-high, the 7XX are the middle, 6XX for the med-low, and the 5XX as entry level. The four-digit models are specialized niche-market models, the 1020 catering to the photography niche, the 1320 for the business users (similar role to the venerable Nokia Communicators and E-series), and the 1520 for the multimedia phablet user.
Therefore, a true successor to the 1020 would expectedly be named the 1030, likely sporting an improved version of the 41-MP sensor, just as the 1020 was the successor to the old 808 (that one used the old, pre-Lumia naming scheme).