No, you should not be changing the limits and doing so will not actually
change anything. If you want more than 64 tuple elements you could have
a tuple whose elements themselves are tuples. For instance if you wanted
256 tuple elements you could program this as a tuple with 64 elements
and each of those elements is a tuple with 4 elements. Or if you like a
tuple with 16 elements and each of those elements a tuple of 16
elements. You get the idea.

Thank you, good Idea! But in my case it was about the support of an old project, therefore a redesign was not my first choice.

Unfortunately, there is only little room for improvement. Microsoft C++ compiler, for example, supports only 127 macro arguments.

After extending BOOST_PP_VARIADIC_SIZE and BOOST_PP_VARIADIC_SIZE_I in boost/preprocessor/variadic/size.hpp and defining additional BOOST_PP_VARIADIC_ELEM_[64..125] as in preprocessor/tuple/elem.hpp BOOST_PP_TUPLE_SIZE() and BOOST_PP_TUPLE_ELEM() work with up to 126 elemnets.

BOOST_PP_TUPLE_TO_SEQ() uses internal some additional macro parameters, it supports tuples with up to 124 elemrnts after adding BOOST_PP_TUPLE_TO_SEQ_[65..124] similar to preprocessor/tuple/to_seq.hpp

No other boost preprocessor macros were changed/tested.