Will the 4GB heap size limit ever be increased?

[claudio]

You probably want to divide by rts_memory_size() which is the number of Wasm memory bytes currently used by the canister (i.e. Wasm MemorySize instruction (Wasm page count) x 65536 (Wasm page size, in bytes)), currently limited by 4GiB since we are using 32-bit wasm.

Some more explanation is here:

Motoko, Array, Memory

First of all, let me point out that constructing an array by repeated concatenation is not something you should do in production code. Since both operands need to be copied for each append, the cost of doing this is quadratic in the size of the final array. Assuming you want an immutable array, a more appropriate way is to create the complete array as mutable, initialise it via mutation, and then freeze it. As for the rts values: memory_size is the current size of the Wasm memory array (mostly…