show delivery estimate in front end order status

You will have to create a custom field of the table "order" via the menu Display->Custom fields.
Then, you will have to edit the file "listing" of the view "order" of the front end via the menu Display->Views and add some code to display the additional information.
You will be able to display the date for the current element like that:

<?php echo $this->row->CUSTOM_FIELD_COLUMN_NAME; ?>


where CUSTOM_FIELD_COLUMN_NAME is the custom field's column name.

I was a bit fast. It should be that code:

<?php echo $row->CUSTOM_FIELD_COLUMN_NAME; ?>


Also, please make sure that you add it in the foreach loop. if you put it at the end like you did, you will only get it once at the end of the table for the last order.

For example you could put it after :
<?php echo hikashop_getDate($row->order_created,'%Y-%m-%d %H:%M');?>

Yes, you have to add your own column for that.
That is standard HTML code...

After the code

<th class="hikashop_order_date_title title" align="center">
					<?php echo JHTML::_('grid.sort', JText::_('DATE'), 'a.order_created', $this->pageInfo->filter->order->dir,$this->pageInfo->filter->order->value ); ?>
				</th>

<th class="hikashop_order_date_title title" align="center">
					<?php echo JHTML::_('grid.sort', 'Delivery estimate', 'a.deliveryestimate', $this->pageInfo->filter->order->dir,$this->pageInfo->filter->order->value ); ?>
				</th>

<td class="hikashop_order_date_value">
						<?php echo hikashop_getDate($row->order_created,'%Y-%m-%d %H:%M');?>
					</td>

<td class="hikashop_order_date_value">
						<?php echo $row->deliveryestimate;?>
					</td>