The general approach taken in the linked questions can be used here, but you'll have to adjust the labelnumber format for unpublished works. For published works, the item total needs to be corrected once the list of unpublished works is printed.
Here is an example that extends to various stages before publication, as indicated by the pubstate field.
\documentclass{article}
\usepackage[american]{babel}
\usepackage{csquotes}
\usepackage[style=numeric,sorting=ydnt,defernumbers]{biblatex}
\makeatletter
\def\forcategory#1{\forlistloop{#1}{\blx@categories}}
\def\ifskipbib{\iftoggle{blx@skipbib}}
\makeatother
% Print labelnumber as item total, minus actual number, plus one
\DeclareFieldFormat{labelnumberwidth}{\iffieldundef{pubstate}{\mkbibbrackets{#1}}{#1}}
\DeclareFieldFormat{labelnumber}{\iffieldundef{pubstate}{\mkbibdesc{#1}}{--}}
\newrobustcmd{\mkbibdesc}[1]{\number\numexpr\value{itemtotal}+1-#1\relax}
\newcounter{itemtotal}
\def\countinit#1{\csnumgdef{count:#1}{0}}
\forcategory{\countinit}
% Add entries to categories, increment entry totals
\def\countadd#1{%
\ifboolexpr{ test {\ifentrytype{#1}} and not test {\ifskipbib} }
{\iffieldundef{pubstate}
{\addtocategory{#1}{\thefield{entrykey}}%
\csnumgdef{count:#1}{\csuse{count:#1}+1}%
\stepcounter{itemtotal}}
{\addtocategory{unpublished}{\thefield{entrykey}}%
\csnumgdef{count:unpublished}{\csuse{count:unpublished}+1}}%
\listbreak}
{}}
\AtDataInput{\forcategory{\countadd}}
\renewbibmacro*{in:}{%
\iffieldundef{journaltitle}{}{\printtext{\bibstring{in}\intitlepunct}}}
\def\defbibtitle#1#2{\csdef{title:#1}{#2}}
\def\defbibsubheading#1{%
\defbibheading{#1}{\subsection*{%
\ifcsundef{title:#1}{\MakeCapital{#1s}}{\csuse{title:#1}}%
\ifnumgreater{\csuse{count:#1}}{1}{~(\csuse{count:#1})}{}%
\ifstrequal{#1}{unpublished}
{\global\defcounter{itemtotal}{\value{itemtotal}+\csuse{count:#1}}}{}}}}
\DeclareBibliographyCategory{article}
\DeclareBibliographyCategory{unpublished}
\DeclareBibliographyCategory{report}
\DeclareBibliographyCategory{inproceedings}
\defbibheading{bibliography}{\section*{Publications and Presentations}}
\defbibtitle{unpublished}{Unpublished articles}
\defbibtitle{inproceedings}{Presentations}
\forcategory{\defbibsubheading}
\begin{filecontents}{\jobname.bib}
@article{submit,
author = {Last, First},
title = {Title},
journaltitle = {Journal},
date = {2012},
pubstate = {submitted}}
@article{inprep,
author = {Last, First},
title = {Title},
date = {2012},
pubstate = {inpreparation}}
\end{filecontents}
\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}
\begin{document}
\nocite{glashow,bertram,chiu,companion,padhye,submit,angenendt,moraux,inprep}
\printbibheading
\bibbycategory
\end{document}

Some notes:
This approach is suited only for use with \nocite in one reference section. Some extensions have been demonstrated in related questions.
The document will typically require an extra LaTeX run to compile, even if biblatex doesn't generate a "rerun LaTeX" warning in the log.
A localization key should be used in the pubstate field. Keys can be redefined in the preamble using \DefineBibliographyStrings. For further details refer to the biblatex manual.
A descending labelnumber emphasizes the total number of works, but here you're counting apples and oranges. This format is probably best suited for CVs with a list of peer-reviewed articles that spans more than one page.