<pre>
\documentclass{article}
\flushbottom
\def\Par{bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla}
ConTeXt:
<pre>
\defineblanksetupalign[aroundfloat][0.8\lineheight plus 3fill minus 0.2\lineheight]\setupfloats[spacebefore=aroundfloat,spaceafter=aroundfloat]\setupwhitespace[0pt plus 1fillline]\prependtoks \vfilll \to \everystoptext
\def\Par{bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla}