\label{sec:PDFfuture}

In the final section of this Report we discuss
three topics that could play an important role in shaping
global analyses of PDFs in the coming years.
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First of all we discuss the problem of theoretical uncertainties
in fits of parton distributions, whose estimate is becoming more
and more urgent given the size of PDF uncertainties in recent
global analysis.
%
Secondly, we summarize recent progress in lattice QCD computations
of PDFs, including the first efforts towards a determination
of their $x$-dependence, and suggest that in the near future lattice inputs
could contribute to global PDF fits.
%
Thirdly, we briefly review the status and plans for future high-energy
colliders, such as the
Large Hadron electron Collider (LHeC) or
the Future Circular Collider (FCC),
and the role that PDFs would play in these.

\subsection{PDFs with theoretical uncertainties}
\input{9-future/subsec-theoreticalunc.tex}

\subsection{Lattice QCD calculations of the proton structure}
\input{9-future/subsec-latticeqcd.tex}

\subsection{Parton distributions at future high-energy colliders}
\input{9-future/subsec-fcc.tex}

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